(1) Field of the Invention
The present invention relates to a ceramic material-reinforced metal-based composite material to be favorably used for machine parts and the like, and to a method for producing the same. Particularly, an alloy is converted to a metal-based composite material by impregnating a semi-molten alloy having a semi-molten alloy in a solid/liquid coexistent state into a preliminarily molded body composed of ceramic whiskers or ceramic particles (hereinafter referred to as xe2x80x9cpreformxe2x80x9d) under pressure, so that various mechanical properties such as the strength and wear resistance of the resulting machine parts are advantageously enhanced.
(2) Related Art Statement
As one of methods for the production of machine parts, a process is known, which arranges a preform in a part of a casting mold cavity (hereinafter cavity) and converts an alloy into a composite material by casing a completely molten alloy composed of a liquid phase alone in the cavity under pressure.
However, it has been recently necessary to reduce the temperature of the alloy melt from the viewpoint of the prolongation of the life of the casting mold including a mold unit and the energy saving.
As a countermeasure to solve the above problem, use of the semi-molten alloy having the solid phase and the liquid phase in a coexistent state may be considered.
As a method for producing a composite material with use of such a semi-molten alloy, a so-called composite casting process is known, in which ceramic whiskers or particles are mixed and stirred into the molten alloy, and the resulting uniform slurry is cast.
However, although this composite casting process is advantageous from the standpoint of reinforcing the entire machine part, but is not suitable for reinforcing a specified part of the machine part.
Further, since the expensive ceramic fibers or particles are also incorporated into such a portion of the machine part as needs no special strength or wear resistance according to the above composite casting process, this process has the demerit that the production cost of the machine part increases.
The present invention is to advantageously solve the abovementioned problem, and to propose a process for advantageously producing a ceramic material-reinforced metal-based composite material which cannot only reduce a casting temperature owing to the use of a semi-molten alloy as an alloy component but also impart a desired characteristic such as strength or wear resistance upon a specified portion of a machine part by arranging a preform at only a specified portion in a cavity and impregnating a semi-molten alloy into the preform under pressure.
Since it has been presumed that the preform would be largely deformed if the semi-molten alloy is impregnated into the preform under pressure, neither research nor development of such a process has been reported heretofore.
Therefore, no example has been reported, in which a machine part was partially reinforced with use of a preform in casting a semi-molten alloy under pressure.
According to the inventors"" researches, it was discovered that even if the semi-molten alloy is used as a starting material, the deformation of the preform can be almost prevented by the optimization of the strength of the preform, the percentage of the in impregnating the semi-molten alloy into the preform under pressure, so that a desired composite material can be produced.
The present invention is based on the above discovery.
That is, the constituent features of the present invention are as follows.
1. A ceramic metal-reinforced metal-based composite material produced by impregnating, under pressure, a semi-molten alloy having a solid phase and a liquid phase coexistent with each other into a preform composed of ceramic whiskers or ceramic particles.
2. A method for producing a ceramic metal-reinforced metal-based composite material, comprising a step of impregnating, under pressure, a semi-molten alloy having a solid phase and a liquid phase coexistent with each other into a preform composed of ceramic whiskers or ceramic particles.
The following 1 to 3 are preferable embodiments of the ceramic metal-reinforced metal-based composite material-producing method. Any combination thereof is also considered as preferable.
1. The preliminarily molded body is arranged in a part or the entire part of a cavity of a mold, and the semi-molten alloy is cast in the cavity under pressure.
2. The percentage of the solid phase in the semi-molten alloy is 10 wt % to 70 wt %.
3. The pressure-impregnating speed of the semi-molten alloy is 1 to 30 cm/s.